NAME

bzero, explicit_bzero — write zeroes to a byte string

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <strings.h>

void
bzero(void *b, size_t len);

void
explicit_bzero(void *b, size_t len);

DESCRIPTION

The bzero() function writes len zero bytes to the string b. If len is zero, bzero() does nothing.

The explicit_bzero() variant behaves the same, but will not be removed by a compiler's dead store optimization pass, making it useful for clearing sensitive memory such as a password.

SEE ALSO

memset(3), swab(3)

HISTORY

A bzero() function appeared in 4.3BSD. Its prototype existed previously in <string.h> before it was moved to <strings.h> for IEEE Std 1003.1-2001 (“POSIX.1”) compliance.

The explicit_bzero() function first appeared in OpenBSD 5.5 and FreeBSD 11.0.

IEEE Std 1003.1-2008 (“POSIX.1”) removes the specification of bzero() and it is marked as LEGACY in IEEE Std 1003.1-2004 (“POSIX.1”). For portability with other systems new programs should use memset(3).